Flexible Solar Panels and "Hard" Dodger Top
I didn't want hard panels here. I wouldn't be able to see over the dodger. Five years ago, when I started planning this, two different companies were touting "new generation" flexible panels, with internal diodes, that would output 100 watts in a footprint that would fit on a dodger.
However, the panels never made it to production and the
companies are out of business.
So I used Unisolar panels.
The structure is a single layer of X Cloth with Mat. This material has two layers of unidirectional fiber, and a single layer of mat. It's all sewn together, and makes it very easy to build up a strong laminate very quickly.
I started with a thin, 1/16" thick fiberglass
shower liner from Home Depot. This stuff comes in 4'x8' sheets, has minimal
fiber reinforcement, and a very glossy finish on one side.
I scuffed all the gloss off with a 36 grit on a grinder. The dodger was covered with a huge sheet of plastic to protect the boat, and the white plastic was
clamped into place.
Then it was covered with fiberglass and epoxy.
I noticed a small sag in the crown. I should have put a support under the whole thing before laying glass, but I didn't think the wet fiberglass would be heavy enough to bend the FRP support.
No big deal, though. I just epoxied a big square piece of fiberglass roving in the center, which raised the area back up.
On top of the X Cloth, I set a single layer of fine mesh fabric, to smooth it out. and then a thin veil, which is just a super thin mat that gives a smooth surface.
After the epoxy kicked and the dodger top had set into the right shape, I cut away the plastic protection, and traced the edge of the existing dodger top onto the bottom of the new fiberglass top.
When finished, the whole assembly will be bolted onto the existing dodger frame.
I drilled the holes now. This will help when measuring and aligning the solar panels.
After that, I covered it with a very thick coat of primer, and then sanded all the primer back off. This filled up a number of small imperfections, from bubbles in the epoxy and whatever.
The flexible panels were set into place, with
much measuring and thinking, and holes were added
for the wires.
Now it's time to make it perfectly smooth, so the finish will look good.
I took it down to my favorite boat yard,
to wet sand it
with an air powered random orbital sander.
I started with 36 grit and worked up to 180.
Then it was wet sanded by hand with 220 grit.
There are still some small surface imperfections,
but I think the primer will fill them.
After cutting it into shape,
I epoxied two layers of X Cloth
on the bottom edges.
This makes the edges about 3/16" thick, will provide
some strength without much weight, and will increase the space under the top.
I want to ensure that there's room under the whole thing, both to hide the wiring and to promote air flow. Air flow is important, to keep mold and mildew from forming on the Sunbrella fabric.
I took the whole thing back to the boat
for a trial fit.
Painting was fun.
I rolled on ten coats of Interlux Ocean Blue Polyurethane. That's the same color as all the other blue stuff on deck. It matches the Pacific Blue Sunbrella.
I wanted a good thick paint job, so that the paint can slowly wear down over the years without requiring a repaint. This single part paint does oxidize and wear down.
Getting the final coat just right took forever.
I kept messing up, and then when I had it just right a bird came along and crapped on it.
I ended up with over 15 coats of paint.
The flexible panels have a sewn-on edge.
I don't know what kind of thread that is, but if they're going to be permanently glued down, I want to cover them so the threads don't have to deal with UV.
I'm going to frame the panels with flexible
vinyl trim, from McMaster-Carr.
It's part number 8323K2, and fits perfectly over the edge. I'm hoping the
vinyl will be UV resistant and won't start looking bad
as the years pass.
The fiberglass top is set up about 1/8",
to allow air to circulate.
Since the Sunbrella dodger is still there,
I don't want mildew to take hold.
This should let everything dry out quickly.
It's offset with nylon washers,
and a little leather pad.
Each panel has a blocking diode, to prevent it from drawing current back out of the batteries at night, or when shaded. The diode is inside a little plastic box.
The box isn't very well constructed, and one of them broke. So I packed all three of them with epoxy and let it set.
Now I know for sure that it's waterproof. That's important for a permanent installation like this.
The leather pads are just punched out of scrap, using a wad punch.
The vinyl trim is also glued down with 5200.
This was a really messy job, and took about eight hours.
I used black 5200, which doesn't come in a fast cure formula. That actually turned out to be a good thing, given the amount of fussing around required to get everything lined up just right.
The panels were glued down using Fast Cure 5200.
5200 is really a polyurethane glue, in my opinion, and I never use it for caulk.
But for an application like this, I wanted a good, thick
flexible glue. Epoxy would have been brittle, and the fiberglass is going
to bend into a different shape when I finally bolt this onto
I've had this leather punch for 30 years, so it deserves a picture.
The three panels are wired in parallel, and the wires are glued closely to the bottom of the fiberglass shell using more 5200.
I sunk a grommet in the
hem of the dodger top.
This will let the wire feed through, underneath
the fiberglass lid, and then run down to the side.
The wire is completely hidden until it gets to the edge of the dodger.
To keep the splices waterproof, they're covered with heat shrink.
For extra protection,
the heat shrink was packed with
marine grade silicone.
As the heat shrink contracted, silicon gooshed out of both ends.
Now I know it's waterproof,
and I feel secure about having it outside in the weather all the time.
The corners were cut
with a utility knife.
I have debated sinking a small bolt through the corners to secure them, but really believe that the 5200 will hold them down through anything.
The 5200 takes
a week to cure.
Time to install it.
I set it in full sun, to check the output with a multimeter.
When the panels are new, the voltage is high.
According to the manual, they'll settle down in a few months. Right now, though,
over 20 Volts, which will
fry the batteries.
It's important to use a charge controller.
These flexible panels output 11 watts maximum.
That is about 30 per cent of what you'll get with a hard panel. However, they
also cost half as much, and are much more tolerant of shade. They also don't
if the boom drops. In full sun, with three panels, I'm getting about 2.5 Amps.
With the boom blocking half of a panel, the output only drops to 2 Amps. That was a surprise.
The front edge is through bolted to the dodger frame. The back edge, though, is held down with screws.
I didn't want bolts on the back edge of the dodger, as the nuts would be guaranteed to take a chunk out of someone's head. Only the two back corners are through bolted.
The charge controller is mounted inside, by the main panel. This controller was recommended by a couple of other boaters. It will handle 15 Amps, can be set for different battery types, and does multistage voltage regulation.
It also has an internal temperature sensor, and separate leads for voltage sensing. I haven't hooked those up, as I want to see how it behaves sensing voltage from the charging wires.
I'm going to add another 80 Watts of hard panels on the stern rails, so the extra capacity will come in handy. I'm also going to add a dedicated blocking diode for the dodger top panels, just in case.
All told, this worked out very nicely. They're very low profile, unobtrusive, and won't break if the boom falls down on them.
We'll see how they hold up in the years to come.